That is what I think so. I will use an HOW and wire it to VFD main disconnect so whenever some body wants to turn it off he can do locally. I am not sure if the control system is also acceptable since my motors can turn on and off using DCS and I can send a signal from HOA to turn the motor on and off.
As was said A HOA is not a safety disconnect and can not be used as one since a VFD can start a motor even if the HOA is in the off position if a malfunction occurs, the only legal disconnect at the motor is an actual disconnect that disconnects the motor from its supply lines, this is also the only legal method that OSHA will accept should someone get hurt they can fine your company a lot of money if you do not have a lockable disconnect at the motor, not including all the law suits that may arise from someone being injured because of you taking this shortcut, also since most VFD's do not like to be unloaded while on you should have a micro switch in the disconnect that turns off the VFD just before the disconnect opens, you can do as you want but like I said you will be in allot of trouble if OSHA ever investigates an injury cause by this motor, also a disconnect must have a means of lock out so that your plant can use the lock out and tag out safety procedures that OSHA requires, a HOA does not allow this as it does not remove the possibility of the drive from supplying power to the motor if something in the control system was to go wrong.
Just having a HOA in the main contactor circuit will not guarantee that another maintenance person can not push in the main contactor energizing the motor and getting someone hurt as it will make the lock out tag out useless, this is also why the NEC and OSHA requires a regular disconnect at the motor for workers to lock out on that keeps others from being able to turn on the motor, so again install a disconnect at the motor just order one with the micro switch already in it, with a break before disconnect feature for the VFD drive which is what we have on all our motors on VFD's.
Sorry but we have to tell you what is required not what you want to hear.
If you have other motors that only have a HOA at the motor then they need to be updated also or you may get a big surprise if OSHA ever visits your plant, trust me the fines are not cheap and in most cases will be 10 times what it would cost installing the correct disconnects at each motor.